The present invention relates to apparatus for magnetically recording events being measured or metered. Electric utility companies use magnetic recorders for billing and survey applications. Typically, a conventional rotating disc electrical power or energy meter is equipped with a pulse initiator for generating a train of electrical pulses representative of the quantity being measured, such as predetermined amounts of real or reactive power that have been consumed (or transmitted). These pulses are then recorded on a magnetic recorder having a tape moving at a very slow rate, such as 1.75 in. every fifteen minutes. To read a meter, the tape is replaced, and it is read by a "translator" at a remote location.
Utility companies commonly interconnect their power feed lines with one another so that if a demand is made on one utility that is above its present operating capacity, power may be drawn from the second utility. Such an interconnection is called an "intertie". Energy flowing between the utilities must be measured so that a record can be kept indicating which utility used what quantities of power during given time periods. The measurement of power is sometimes accomplished by a meter having a detent in the disc such that it will rotate only in one direction. Two of these meters are then used, with one meter measuring power transfer from the first utility to the second, and the other meter measuring power transfer from the second utility to the first.
If it is desired to record demand and usage in units of time, the electric meters are equipped with pulse initiators. These are devices which generate electrical pulses or signals having a repetition rate representative of the quantity of the parameter being measured. For example, the pulse initiator may generate an electrical pulse for each revolution of the rotating disc on a conventional power meter.
There are a number of magnetic recorders available for billing or survey applications. For example, there are two-track and four-track magnetic recorders which are commercially available for use in these applications. In either case, one track is used for recording time pulses or marks, leaving either one or three tracks available for recording data, depending upon the instrument selected.
If conventional billing recorders were used at a utility intertie, four energy meters would be required, two for real power (Kw) and two for reactive power (KVAR). Even in such a system, four separate data tracks would be required for complete recording of the parameters being measured. Since one track is required for time marks or pulses, a commercially available four-track recorder would not be sufficient to record all the data required at an intertie.
The present invention overcomes this difficulty by recording two separate inputs (such as reactive power from the two utilities) on a single data track on the recorder. A device which receives signals from pulse initiators associated with electric meters and accumulates them for recording on a magnetic cartridge is referred to as a "totalizer". The present invention is thus directed to a totalizer receiving data from two separate inputs for recording that data on a common data track of a magnetic recorder or other non-volatile memory, such as a "bubble" memory.
The totalizer generates a train of recording pulses at a predetermined "offset" repetition rate, preferably chosen in the mid range of the channel capacity of the recorder. For example, if the data track of the recorder is capable of recording 6,000 pulses per hour, the offset repetition rate may be chosen to be 3,000 pulses per hour. If both inputs are recording no transfer of power, the totalizer will record pulses on the common data track at a rate of 3,000 pulses per hour. The totalizer increases the repetition rate of the recording pulses above the offset rate in response to an increase in the repetition rate of signals received from one of the sources; and it decreases the repetition rate of the recording pulses below the offset rate in response to an increase in the repetition rate of the signals received from the other source. Thus, the totalizer of the present invention provides a bidirectional capacity in that it enables the recorder to record events from two sources on a single data track.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.